The humble kangkong (water spinach) has a reputation in Malaysia for being a cheap dish, but in the past few days, it has become the hottest vegetable in town.

Social media was awash with photos of the leafy vegetable fried with belacan (shrimp paste), while some complained that the sudden demand had caused some restaurants to run out of kangkong.

This came after Prime Minister Najib Razak complained that Malaysians blame the government when prices go up but do not give it credit when prices go down.

"Today, I read in the newspaper that the prices of some things have dropped. The price of kangkong increased before this and now it has gone down," he was quoted as saying in the online media on Sunday.

"When this happens, they don't want to praise the government. But when it rises, they blame the government... This is not fair as it is due to weather conditions."

Kangkong, sometimes called "water spinach", is cheap as it grows profusely, sometimes in unappetising places like drains.

The prime minister's statement triggered an immediate backlash on social media, unleashing the creative juices of Malaysians who posted kangkong jokes at his expense and that of the government.

Some examples: A Kentucky Fried Chicken (KFC) advertisement modified to show Najib as Colonel Sanders with the tagline "Kangkong Fried Belacan (KFB)". A movie poster showing King Kong embracing the Putra World Trade Centre while clutching a bunch of kangkong with the tagline "King Kang Kong".

Then, there was the "McKangkung", a burger stuffed full of kangkong.

These jokes carry a sting in their tail because many Malaysians found the kangkong remark insulting. The prime minister, they felt, was asking them to lower their living standards.

Najib's actual complaint - that the people sometimes blamed the government for matters beyond its control - was soon lost.

Political analyst Ibrahim Suffian, who runs the pollster Merdeka Centre, said many Malaysians do not really understand why the government recently cut subsidies for fuel, sugar and electricity, nudging up the cost of living across the board.

"The government had long given an image of omnipotence with the ability to control prices. Now, it's suffering from a credibility issue," he said.

The backlash is reminiscent of the reaction after the government called on the people to "change their lifestyle" when fuel prices soared in 2007.